Malaria kills over a million people a year, mostly in Sub-Saharan Africa where the infected mosquito population is out of control. Now, epidemiologists are developing a radical new mechanism for vaccinating at-risk populations: through mosquito bites.

Researchers at Radboud University in Nijmegen, the Netherlands, staged a small proof-of-principle experiment, aimed at determining whether exposure to parasites, via insect bites, could vaccinate humans against malaria.

Knowing that humans can develop an immunity to malaria after repeated exposures and that the drug chloroquine kills malaria parasites in the late stages of infection, the researchers divided 15 subjects into two groups. They exposed the first group, periodically, to parasite-bearing mosquitoes and treated them with chloroquine. The second group, the researchers also treated with chloroquine, but didn't expose to the mosquitoes. All the volunteers stopped taking chloroquine and were later exposed to parasite-carrying mosquitoes. No members of the group previously exposed to malaria developed the disease; each member of the comparison group did.

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Although it's a far cry from delivering an actual vaccine via insect — and seems more a call for widerspread distribution of antimalarial drugs — it does present the possibility that insects could someday be used to immunize populations against disease. With respect to pandemics like malaria, such a mechanism could be a lifesaver, but it also presents a profound ethical dilemma. The subjects in this test gave their consent to be infected, persons living among vaccine-carrying critters wouldn't have the same luxury.